Vref on tube booster (pedal i designed) is ~3.5v instead of 4.5v

[antonis]

the 9v regulator will provide a constant voltage to that section of the circuit despite any current draw. that holds true even if you supply it with 9V.

Nope. See dropout voltage.

Both you guys are right..!!

To be more specific: Any series voltage regulator develops at its output a voltage lower than the one at its input by a dropout voltage, at least..!!
The above means that a 9V regulator needs a voltage equal to (or higher than) 11V (assuming 2 V dropout) for a regulated 9V output..
In case of input voltage lower than 11V, its output develops an unregulated voltage equal to Vin - dropout..
(e.g. a 9V regulator fed with 9V will exhibit 7V at its output..)
It effectivelly acts as a voltage drop series resistor..

P.S.
Minimum dropout voltage is strongly dependent on current draw (in cojunction with unregulated voltage filtering, of course)..
One can get regulated 9V with an input voltage as low as 10V, or so, for an "open" load circuit..
 

[snow123]

the 9v regulator will provide a constant voltage to that section of the circuit despite any current draw. that holds true even if you supply it with 9V.

Nope. See dropout voltage.

Both you guys are right..!!

To be more specific: Any series voltage regulator develops at its output a voltage lower than the one at its input by a dropout voltage, at least..!!
The above means that a 9V regulator needs a voltage equal to (or higher than) 11V (assuming 2 V dropout) for a regulated 9V output..
In case of input voltage lower than 11V, its output develops an unregulated voltage equal to Vin - dropout..
(e.g. a 9V regulator fed with 9V will exhibit 7V at its output..)
It effectivelly acts as a voltage drop series resistor..

P.S.
Minimum dropout voltage is strongly dependent on current draw (in cojunction with unregulated voltage filtering, of course)..
One can get regulated 9V with an input voltage as low as 10V, or so, for an "open" load circuit..

so im assuming it would be best to use a 5v regulator for the relay section?

[snow123]

and honestly, at this point im thinking it would be better to re-design the PCB.

would this kind of thing work?

the more i look at your flip flop, the more i wonder if D21 and D20 are the issue. why did you include them?

honestly i was just copying this pedalpcb relay thing: https://docs.pedalpcb.com/project/BasicRelayBypass-PedalPCB.pdf

and according to this, D20 & D21 are used to prevent voltage spikes.

[antonis]

so im assuming it would be best to use a 5v regulator for the relay section?

I think it's to early (we're in 5^th page only) to make such a conclusion..

[antonis]

and according to this, D20 & D21 are used to prevent voltage spikes.

Could you plz study again what author says in Power section..??

[snow123]

and according to this, D20 & D21 are used to prevent voltage spikes.

Could you plz study again what author says in Power section..??

yep, ill add a separate diode for the switching.

[antonis]

yep, ill add a separate diode for the switching.

I'm talking about voltage divider..

[snow123]

yep, ill add a separate diode for the switching.

I'm talking about voltage divider..

im not using it for the rest of the circuit though.

and this is what that bit of the circuit looks like now:

[bartimaeus]

and honestly, at this point im thinking it would be better to re-design the PCB.

would this kind of thing work?

the more i look at your flip flop, the more i wonder if D21 and D20 are the issue. why did you include them?

honestly i was just copying this pedalpcb relay thing: https://docs.pedalpcb.com/project/BasicRelayBypass-PedalPCB.pdf

and according to this, D20 & D21 are used to prevent voltage spikes.

in that case, i'd jumper D20 to avoid its voltage drop. major manufacturers like earthquaker don't bother with those diodes. i know earthquaker has made some questionable design choices, but they've made (tens of?) thousands of pedals with relays, and i never hear about a broken one.

and according to this, D20 & D21 are used to prevent voltage spikes.

Could you plz study again what author says in Power section..??

yep, ill add a separate diode for the switching.

notice the author says that others have had issues. seems clear that pedalpcb is one of those people, and pedalpcb's solution was to use a regulator.

also to go a bit off topic, i don't love the author's choice of a 555 for the flip flop. dedicated flip flop chips have been common for decades after all. CD4013B for example.

yep, ill add a separate diode for the switching.

I'm talking about voltage divider..

im not using it for the rest of the circuit though.

and this is what that bit of the circuit looks like now:

looks good to me.

the 78L05 and the 78L09 have the same package, so you can buy both and see which works best.

[snow123]

ok, are there any other general improvements i could make to the circuit? or any potential issues that might need fixing?

[bartimaeus]

the relay section seems ok now.

the only changes i'd make would be to prevent pop. i'd swap the locations of R1 and C1 so you don't have a cap connected directly to the jack.

i'd similarly add a 100R resistor between C12 and the switch. i'd do the same for C50 and the switch.

you may also want a cap between Q1 and the relay switch. an easy solution would be to move C50 to be directly after Q1, so it's before either switch.

you could probably leave out R17, it just seems to limit the max possible volume a tiny bit?

[PRR]

...swap the locations of R1 and C1 so you don't have a cap connected directly to the jack....

No difference.

[antonis]

...swap the locations of R1 and C1 so you don't have a cap connected directly to the jack....

No difference.

bartimaeous is fun of Mr. Black's "theory"..
https://www.mrblackpedals.com/blogs/straight-jive/6629778-what-really-causes-switch-pop

[bartimaeus]

...swap the locations of R1 and C1 so you don't have a cap connected directly to the jack....

No difference.

bartimaeous is fun of Mr. Black's "theory"..
https://www.mrblackpedals.com/blogs/straight-jive/6629778-what-really-causes-switch-pop

ah, so it is unnecessary? no need to poke fun, please send a better explanation if you find one.

when i tested my own pedals with very little switch pop, all of those pedals had series resistors on the input and output. for example this aion pedal: https://aionfx.com/app/files/docs/emerald_documentation.pdf


EDIT: regardless, i'd still strongly recommend moving C50 to be directly after Q1. because you can have a dc offset at the emitter of Q1, which will can cause some noticeable pop from the RelayB switch.

[antonis]

No intention for mocking or poking fun..

As I already told you here: https://www.diystompboxes.com/smfforum/index.php?topic=129962.0, Mr. Black's aspect isn't recognized as prestigious..

As for the IN/OUT series resistors, it's just a matter of taste..

[bartimaeus]

No intention for mocking or poking fun..

As I already told you here: https://www.diystompboxes.com/smfforum/index.php?topic=129962.0, Mr. Black's aspect isn't recognized as prestigious..

As for the IN/OUT series resistors, it's just a matter of taste..

you told me it is not prestigious. but you didn't say the reason?

a lot of what mr black says seems to be rephrasing of this post (which i just saw in another thread): http://www.muzique.com/lab/pop.htm

[antonis]

you told me it is not prestigious. but you didn't say the reason?

I presume you're a recent reader or you should remember the numerous posts/comments on the end of the page..
(magically vanished some day...)

Anyway, much ado about nothing..
:beer: :beer: :beer:

[duck_arse]

the only changes i'd make would be to prevent pop. i'd swap the locations of R1 and C1 so you don't have a cap connected directly to the jack.

in the diagram shown, C1 and R1 are in series. series components the order doesn't matter. cap against jack makes no difference to speed of charge or voltage level or anything else. even with an added pulldown resistor hard against tip in, the C1 and R1 order is immaterial.

Mr Black doesn't mention series components, does he? also, if you are going to give the straight jive, you should not be posting diagrams like Grounded_True-Bypass.png where people can see it, as the switch is drawn in impossible mode. your switch sense needs to make sense before the diagram can make sense.


::cider::

[dig it:] also, switch in Grounded_True-Bypass_with_Current_Limiting.png is wrong, can't make sense.

[bartimaeus]

the only changes i'd make would be to prevent pop. i'd swap the locations of R1 and C1 so you don't have a cap connected directly to the jack.

in the diagram shown, C1 and R1 are in series. series components the order doesn't matter. cap against jack makes no difference to speed of charge or voltage level or anything else. even with an added pulldown resistor hard against tip in, the C1 and R1 order is immaterial.

Mr Black doesn't mention series components, does he? also, if you are going to give the straight jive, you should not be posting diagrams like Grounded_True-Bypass.png where people can see it, as the switch is drawn in impossible mode. your switch sense needs to make sense before the diagram can make sense.


::cider::

[dig it:] also, switch in Grounded_True-Bypass_with_Current_Limiting.png is wrong, can't make sense.

thanks very much for explaining! i'll avoid straight jive in the future.

moving on, don't you agree that the position of the RelayB switch in snow123's schematic will likely cause pops? i think he needs the series capacitor after Q1 and R3, before the switch.

[antonis]

moving on, don't you agree that the position of the RelayB switch in snow123's schematic will likely cause pops?

Where do you locate the possible pop..??
(C2, C50 or somewhere else..??)